Joe Vignola, the Democratic Party's endorsed candidate to run against U.S. Sen. John Heinz in the fall, faces a contested primary on April 26, but by the way he talks, you wouldn't know it.

Asked if he was leaning toward any of the Democratic presidential candidates, Vignola said no.

"As the leader of the ticket here in Pennsylvania, I view myself as having the obligation to try to keep unity," he said.

And rather than turn up the pressure on the three others running for the party's nomination to the Senate, the former Philadelphia controller focused his attack on Heinz, the Republican incumbent seeking his third Senate term.

During an interview yesterday, Vignola was unrelenting in his criticism of Heinz's record.

Stating that he would represent "Main Street, Pennsylvania," the 38- year-old Philadelphian said, "John Heinz has lost touch with that Main Street - if he ever had touch with that Main Street."

Vignola said that in Heinz's 16 years in Congress - he was first elected to the House of Representatives in a special election in 1971 - Heinz has authored no legislation of significance.

"Give me something substantial that he shtood for, a bill that bears his name, just like he bears a ketchup bottle name," Vignola said. "You can't tell me."

Heinz's family name and his family wealth have helped him "buy" elections, the challenger said. Even with his wealth and huge campaign treasure chest, Heinz captured "only" 59 percent of the vote in his 1982 re- election bid against a Democrat who was outspent by about 7-1, Vignola said.

For the coming election, Vignola said he has about $200,000 in hand and plans to raise $2 million for the entire race. He said Heinz has not responded to his proposal to limit campaign spending. As of early February, Heinz had already raised $1.36 million.

Regardless of his campaign funding, Vignola said he would be able to win the state by attacking Heinz's record.

He criticized the incumbent for voting to cut education and the U.S. Environmental Protection Agency, while funding expensive military programs. All along, Heinz has supported the major economic goals of the Reagan administration, Vignola declared. He also pointed out that although Heinz has become more independent of the administration in the last year, the senator did support many of the major goals of the Reagan administration.

Reagan has done well getting votes in Pennsylvania, Vignola said, "but that doesn't mean you're doing well for Pennsylvania.

"We have to throw out the Reagan followers, and we have to throw out the Reagan loyalists - and John Heinz is a Reagan loyalist."

In addition, Vignola attacked Heinz for supporting Judge Robert Bork in his bid for the U.S. Supreme Court, for not acting forcefully on long-term health-care issues, for voting to increase the cost of Medicare premiums, and for voting against the highway bill that promised $2 billion in infrastructure construction work to the state.

On that issue, Vignola declared, Heinz was one of 17 U.S. senators to oppose the bill. Then, after it was sent to the president - who vetoed it - Heinz reversed his field and voted to override the veto, he said.

Heinz, he added, "talks tough on trade, but then he goes out and imports lumber to build a vacation home" in Idaho.

Furthermore, Vignola attacked Heinz for being an "obstacle" to divestment in South Africa. As a member of the pension board in Philadelphia, Vignola said, he helped see that the city's moneys were divested.

As controller, he claimed to have pinpointed $500 million in waste in the $25 billion in city budgets. Vignola said that he also gained a reputation for honesty and integrity by attacking patronage and nepotism among his fellow Democrats. He said he cracked down on "deadbeats" that did business with Philadelphia and stated, "We have to do the same thing to people who are not paying the federal government." The government has $100 billion in unpaid loans and bills, he said.

If elected, Vignola said he would attempt to link federal, state and local government money with private money to target "core industries" such as steel. For instance, he said, using a "cross between revenue sharing and UDAG (Urban Development Action Grants) grants," the Homestead steel mill could stay open, saving 5,000 jobs.

He said he also would stand up for day-care legislation and a long-term care bill that would be financed by removing the cap on Medicare deductions. By increasingthe cost of Medicare to individuals making more than $45,000 annually, he said, all senior citizens needing long-term nursing home, hospice or home care could have it - without further adding to the federal deficit.

Vignola said he would improve the government's balance sheet by opposing the MX missile and all funding for the "Star Wars" space-based missile defense system. The $30-billion system, he said, is too expensive and will force the Soviet Union to step up the pressure on the arms race.